This invention relates to methods of erecting formwork for pouring a slab in place on steel joists.
The invention is especially concerned with methods of erecting framework for pouring a concrete slab in place on steel joists of the type in the form of a Warren truss, comprising a web and top and bottom chords. The web generally comprises a steel bar bent to zigzag form and each of the top and bottom chords comprises a pair of angle bars (or other suitable shapes) welded to opposite sides of the web. The joist may be a standard steel joist or a so-called composite joist in which the peaks of the web extend up above the top chord. Such a composite joist, wherein the chords are made of angle bars, may have its top chord angle bars either upright (i.e., with their horizontal legs at the top), or inverted as shown in U.S. Pat. No. 3,362,121. Heretofore it has been the usual practice to lay the formwork for the pouring of a concrete slab on the horizontal legs of the top chord angles, the formwork being constituted, for example, by corrugated steel plate or plywood, which remains in situ after the slab has been poured. With the cost of steel plate (or other in-place forms or centering) being what it is today, this practice is quite costly.